Membrane fusion events, while commonplace in normal cell biological processes, are also involved in a variety of disease states, including, for example the entry of enveloped viruses into cells. Peptides are known that inhibit or otherwise disrupt membrane fusion-associated events, including, for example, inhibiting retroviral transmission to uninfected cells. As an example, the synthetic peptides DP-107 and DP-178 derived from separate domains within the human immunodeficiency virus type 1 (“HIV-1”) transmembrane (“TM”) glycoprotein gp41, are potent inhibitors of HIV-1 infection and HIV induced cell—cell fusion.
Lambert, et al., “Peptides from Conserved Regions of Paramyxovirus Fusion (F) Proteins are Potent Inhibitors of Viral Fusion,” Proc. Natl. Acad. Science U.S.A., Mar. 5, 1996, Vol. 93 (5), pp. 2186–91, discloses that the synthetic peptides DP-107 and DP-178 (T-20), derived from separate domains within the human immunodeficiency virus type 1 (HIV-1) transmembrane (TM) protein, gp41, are potent inhibitors of HIV-1 infection and fusion. Using a computer searching strategy (computerized antiviral searching technology, C.A.S.T.) based on the predicted secondary structure of DP-107 and DP-178 (T-20), Lambert, et al. identified conserved heptad repeat domains analogous to the DP-107 and DP-178 regions of HIV-1 gp41 within the glycoproteins of other fusogenic viruses. Antiviral peptides derived from three representative paramyxoviruses, respiratory syncytial virus (RSV), human parainfluenza virus type 3 (HPIV-3), and measles virus (MV) blocked homologous virus-mediated syncytium formation and exhibited EC50 values in the range 0.015–0.250 μM. Moreover, these peptides were highly selective for the virus of origin.
U.S. Pat. Nos. 6,013,263, 6,017,536 and 6,020,459 incorporated herein in their entirety, likewise disclose that the 36 amino acid peptide DP178 corresponding to amino acids 638 to 673 of gp41 from the HIV-1 isolate LAI (HIV-1LAI), and the 38 amino acid peptide DP107 corresponding to amino acids 558–595 of gp41 from the HIV-1LAI, both exhibit potent anti-HIV-1 activity.
While many of the anti-viral or anti-fusogenic peptides described in the art exhibit potent anti-viral and/or anti-fusogenic activity, these peptides suffer from short plasma half-lifes in vivo, primarily due to rapid serum clearance and peptidase and protease activity. This in turn greatly reduces the effective anti-viral activity of the peptides. There is therefore a need for a method of prolonging the half-life of existing anti-viral and/or anti-fusogenic peptides and providing for longer duration of action of these peptides in vivo.